1. Technical Field
The present application relates generally to carbon nanotube fabrics and methods of making same for use in heat emitting systems, and, more specifically, to the utilization of such nanotube heating elements for the changing of phases of a material, such as a chalcogenide material.
2. Discussion of Related Art
Small heating elements are useful for many applications such as changing the phase of chalcogenide memory devices. The use of electrically writable and erasable phase change materials (i.e., materials which can be electrically switched between non-crystalline and crystalline states or between different resistive states while in crystalline form) for electronic memory applications are known in the art and are disclosed, for example, in U.S. Pat. No. 6,635,951 to Zahorik, the entire contents of which are incorporated herein by reference.
There is an ever-greater need for smaller-scale devices. Carbon nanotubes (NTs) are being used in many different applications in the field of electronics and are found to be useful due to their electrical (i.e. conducting or semi-conducting), mechanical, optical, chemical and thermal properties.
Carbon nanotubes, with tube diameters around 1-2 nm, are electrical conductors that are able to carry extremely high current densities, see, e.g., Z. Yao, C. L. Kane, C. Dekker, Phys. Rev. Lett. 84, 2941 (2000), the entire contents of which are incorporated herein by reference. They also have the highest known heat conductivity, see, e.g., S. Berber, Y.-K. Kwon, D. Tomanek, Phys. Rev. Lett. 84, 4613 (2000), and are thermally and chemically stable, see, e.g., P. M. Ajayan, T. W. Ebbesen, Rep. Prog. Phys. 60, 1025 (1997), the entire contents of which are incorporated herein by reference. Due to their properties, carbon nanotubes have been shown to emit heat due to resistive current conduction.
Using individual nanotubes for heat emission, however, can be problematic because of difficulties in growing them with suitably controlled orientation, length, and the like.
There is a need in the art for very efficient, very small, even submicron-sized heat transfer elements which are easily fabricated and are compatible with electronics applications and fabrication techniques. There is likewise a need in the art for large scale fabrication methods of nanoscale heat emitters used for electronic applications in the semiconductor industry which can be monolithically integrated into a CMOS or similar process flow to fabricate integrated circuits. Rapid cycling of heating elements would provide a technique for switching the states of materials. In certain applications it might be beneficial to allow heat transmission to occur for extended periods of time with exquisite temperature control. Naturally, the uses of such elements extend to most types of consumer electronics where heat emission in integrated elements is beneficial.